Moving picture compression/expansion apparatus

ABSTRACT

A moving picture compression apparatus in which signal deterioration can be minimized on repeated compression/expansion. The moving picture compression apparatus compresses a moving picture signal having a motion vector multiplexed in its blanking portion and includes a motion vector separator  13  for separating the motion vector multiplexed in the blanking portion of the moving picture signal and components from a difference calculating unit  2  to a motion compensation unit  10  for compressing the moving picture signal using the motion vector.

This is a continuation of application Ser. No. 08/926,164, filed Sep. 9,1997, now U.S. Pat. 6,418,167.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a moving picture compression apparatus and amoving picture expansion apparatus suitable for a system fortransmitting or storing moving picture signals, such as a digitaltelevision broadcasting equipment or a digital video disc.

2. Description of the Related Art

In a system for transmitting or storing digital moving picture signals,picture signals are encoded (compressed) by exploiting intra- orinter-frame correlation of moving picture signals for efficientutilization of a transmission channel or a storage medium. As encoding(compression) techniques for moving picture signals, there is known acompression system standardized by a research organization termed MovingPicture Experts Group (MPEG) for encoding moving pictures for storage.

In the method for compressing picture signals by exploiting theintra-frame correlation, orthogonal transform, such as discrete cosinetransform (DCT), capable of concentrating coefficients for encoding, ispredominantly employed.

In the method for compressing picture signals by exploiting theinter-frame correlation, so-called motion-compensated inter-frameprediction is predominantly employed. The principle of themotion-compensated inter-frame prediction is now explained by referringto FIG. 1. It is assumed that pictures P1 and P2 have been generated attime pints t1 and t2, respectively, with the picture P1 having beentransmitted and with the picture P2 being about to be transmitted, asshown in FIG. 1. The picture P2 is split into plural blocks for each ofwhich the amount of motion (motion vector) between it and the picture P1is detected. The motion-compensated inter-frame prediction resides infinding a difference picture between a prediction picture and the blockof the picture P2 and encoding the difference picture and the motionvector. The prediction picture corresponds to the picture P1 moved intranslatory movement a distance equal to the motion vector.

FIGS. 2 and 3 shows a conventional moving picture compression devicewhich takes advantage of the above-described intra- and inter-framecorrelation, and the structure of a conventional moving pictureexpansion device, respectively.

The conventional moving picture compression device, shown in FIG. 2,compresses the input digital picture signal entering a picture inputterminal 101 to output the compressed signal at a bitstream outputterminal 109.

In the conventional moving picture compression device, shown in FIG. 2,the picture signals entering the picture input terminal 101 is routed toa motion vector detector 112 where the motion vector is calculated. Themotion vector information as found by the motion vector detector 112 issent to a motion compensation unit 110 which then motion compensates apicture stored in a frame memory 111, based on the motion vector, forformulating a prediction picture.

The digital picture signals entering the picture input terminal 101 arealso routed to a difference calculation unit 102 which then calculatesthe difference between the picture signals entering the picture inputterminal 101 and the prediction picture formulated by the motioncompensation unit 110. The difference signal, thus found by thedifference calculation unit 102, is routed to an orthogonal transformunit 103 for orthogonal transform. The signal orthogonal transformed bythe orthogonal transform unit 103 is routed to a quantizer 104 where itis quantized for compression. The quantized data is routed to amultiplexer 108 where it is multiplexed with the motion vectorinformation and outputted at a bitstream output terminal 109.

The data quantized by the quantizer 104 is also routed to a dequantizer105 where it is dequantized and then inverse orthogonal transformed byan inverse orthogonal transform unit 106. This produces the samedifference picture as that restored from the output bitstream. Thesignal of the difference picture and the signal of the predictionpicture formulated by the motion compensation unit 110 are summedtogether by an adder 107 to produce picture signals which are entered tothe frame memory 111 for the above-mentioned motion compensation.

On the other hand, the conventional picture expansion device shown inFIG. 3 expands a bitstream entering an input terminal 121 to output theexpanded bitstream at a picture output terminal 126.

Referring to FIG. 3, the bitstream entering an bitstream input terminal121 is sent to a motion vector separator 122 where the motion vectorinformation is separated from the bitstream. This motion vectorinformation is sent to a motion compensation unit 127 which then motioncompensates a picture in the frame memory 128 for constructing aprediction picture.

The quantized data taken out of the bitstream by the motion vectorseparator 122 is routed to a dequantizer 123 for dequantization andthence supplied to an inverse orthogonal transform unit 124 for inverseorthogonal transform to generate a difference picture. The signals ofthe difference picture and those of the prediction picture produced bythe motion compensation unit 127 are summed together by ah adder 125 toproduce picture signals which are stored in a frame memory 128 whilebeing outputted at the picture output terminal 126.

The moving picture compression device and moving picture expansiondevice, as described above, are occasionally connected in series to eachother, as shown in FIG. 4. The compression and expansion devices, thusinterconnected in tandem, as shown in FIG. 4, are equivalent to a devicefor repeatedly executing compression and expansion.

Specifically, the picture signals supplied to a picture input terminal200 in FIG. 4 are compressed by a moving picture compression device 201and outputted at a bitstream output terminal 202. This bitstream issupplied by for example broadcasting, communication or recording mediumto a bitstream input terminal 220 and expanded by a moving pictureexpansion device 221 so as to be outputted at a picture output terminal222. The picture signals, outputted at the picture output terminal 222,are entered via for example an edition unit, not shown, to a pictureinput terminal 240. The moving picture signals supplied to the pictureinput terminal 240 are compressed by a moving picture compression device241 so as to be outputted at a bitstream output terminal 242. Thisbitstream is supplied by for example broadcasting, communication orrecording medium to a bitstream input terminal 260 and expanded by amoving picture expansion device 261 so as to be outputted at a pictureoutput terminal 262. The picture signals outputted at the picture outputterminal 222 are sent to for example the edition unit for edition.

In the arrangement shown in FIG. 4, the moving picture compressiondevice 201 and the moving picture expansion device 221 execute firstcompression/expansion, while the moving picture compression device 241and the moving picture expansion device 261 execute secondcompression/expansion. The same holds for the third and followingcompression/expansion operations.

If the picture is repeatedly compressed/expanded by the above-describedcompression/expansion system, the picture quality is deteriorated eachtime the operations are repeated.

Thus it is said to be advisable to match the picture coding type at thetime of compression for suppressing picture quality deteriorationbrought about by repeated compression/expansion. That is, picturequality deterioration is thought to be suppressed by using the sameencoded picture type, that is the intra-coded picture or I-picturedevoid of motion compensation, a forward predictive encoded picture orP-picture obtained on motion compensation from a temporally previousframe or a bidirectional prediction encoded picture or B-pictureobtained on motion compensation from a temporally previous frame and atemporally succeeding frame, as that used for the moving picturecompression device 201 and the moving picture compression device 241 ofFIG. 4, from one frame to another.

It is also contemplated to set in store the motion vector and allparameters, such as quantized parameters for orthogonal transform.Specifically, the motion vector and all parameters, such as quantizedparameters for orthogonal transform, in the moving picture compressiondevice 201 in FIG. 4, are laid in store so as to be used in the movingpicture compression device 241. If the motion vector and all parameters,such as quantized parameters for orthogonal transform, are laid in storein this manner, it becomes unnecessary to perform motion predictionagain or re-quantization at the time of re-compression thus eliminatingpicture quality deterioration on repeated compression/expansion.

It has however been found experimentally that simply matching thepicture coding type at the time of repeated compression/expansion stillleads to significant deterioration such that picture quality isdeteriorated each time the compression/expansion operations arerepeated.

On the other hand, if the information such as the motion vector and allparameters, including quantized parameters for orthogonal transform, arelaid in store, it becomes necessary to provide a separate recordingmedium for storage of the information, thus complicating the devicestructure. Moreover, the value laid in store are not necessarily optimumvalues, while the information volume is excessive for storage.

As described above, repeated compression/expansion of the picture by themoving picture compression/expansion method exploiting the conventionalmotion compensated inter-frame prediction leads to picture qualitydeterioration for each compression/expansion, while there has not beenknown a drastic method for overcoming this drawback.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide a movingpicture compression device and a moving picture expansion device wherebyit becomes possible to suppress picture quality deterioration otherwiseproduced on repeated compression/expansion.

In one aspect, the present invention provides a moving picturecompression device including motion vector separating means forseparating a motion vector multiplexed in a blanking portion of a movingpicture signal and compression means for compressing the moving picturesignal using the motion vector.

In another aspect, the present invention provides a moving pictureexpansion device including motion vector separating means for separatinga motion vector supplied in a state of being appended to the compressedmoving picture signal, expansion means for expanding the compressedmoving picture signals using the separated motion vector andmultiplexing means for multiplexing the separated motion vector in theblanking portion of the expanded moving picture signal.

According to the present invention, the motion vector used in the movingpicture expansion device is multiplexed in a blanking portion of thepicture signal and the moving picture expansion device uses the motionvector multiplexed in the blanking portion for compressing the picture,for evading the use of an inappropriate motion vector on the occasion ofrepeated compression/expansion.

More specifically, according to the present invention, the motion vectorused in the moving picture expansion device is multiplexed in theblanking portion of the picture signals and outputted, while the movingpicture compression device effects picture compression using the motionvector multiplexed in the blanking portion, so that there is no risk ofan inappropriate motion vector being used for repeatedcompression/expansion, thus minimizing the signal deteriorationotherwise caused by repeated compression/expansion.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates the principle of motion-compensated inter-frameprediction.

FIG. 2 is a schematic block circuit diagram showing the structure of aconventional moving picture compression device.

FIG. 3 is a schematic block circuit diagram showing the structure of aconventional moving picture expansion device.

FIG. 4 shows the state of connection of the moving picture compressiondevice and the picture expansion device.

FIG. 5 is a schematic block circuit diagram showing the structure of amoving picture expansion device according to a first embodiment of thepresent invention.

FIG. 6 illustrates a blanking in which to multiplex the motion vectorinformation.

FIG. 7 is a schematic block circuit diagram showing the structure of amoving picture expansion device according to a first embodiment of thepresent invention.

FIG. 8 is a schematic block circuit diagram showing the structure of amoving picture expansion device according to a second embodiment of thepresent invention.

FIG. 9 is a schematic block circuit diagram showing the structure of amoving picture expansion device according to a third embodiment of thepresent invention.

FIG. 10 is a schematic block circuit diagram showing the structure of amoving picture compression device according to the third embodiment ofthe present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to the drawings, preferred embodiments of the presentinvention will be explained in detail.

Referring to FIG. 5, a moving picture expansion device of the presentembodiment includes a multiplexer 29 for multiplexing the motion vectorin a blanking portion of picture signals for storage. Referring to FIG.7 the moving picture compression device of the present embodimentincludes a motion vector separator 13 for separating the motion vectormultiplexed in the blanking portion of the picture signals by the movingpicture expansion device of FIG. 5.

That is, in the first embodiment of the present invention, the motionvector information as found by the preceding picture compression andsupplied to the expansion device is multiplexed in the blanking portionof the expanded picture and outputted so that, at the time of thesubsequent picture compression, the motion vector multiplexed in theblanking portion is separated and used. Thus, in the present firstembodiment, there is eliminated the necessity of performing a complexoperation of setting the motion vector in store and providing a separaterecording medium for setting the motion vector in store.

Referring to FIG. 5, a moving picture expansion device according to thefirst embodiment of the present invention is explained.

The moving picture expansion device of the first embodiment of thepresent invention inputs a bitstream at an input terminal 21 and outputsat a picture output terminal 26 a moving picture signal in the blankingportion of which the motion vector is multiplexed.

Referring to FIG. 5, the bitstream entered at the bitstream inputterminal 21 is of the format for compression encoding for movingpictures, such as MPEG standard, and contains the motion vector detectedat the time of compression encoding of the moving pictures in additionto the compressed moving picture signals. This bitstream is sent to amotion vector separator 22 where the motion vector information isseparated from the bitstream. This motion vector information is sent toa motion compensation unit 27. The motion compensation unit 27 motioncompensates the picture in the frame memory 28 based on the motionvector for constructing a prediction picture.

The quantized data (compressed moving picture signals) taken out fromthe bitstream by the motion vector separator 22 is sent to a dequantizer23 for dequantization and thence supplied to an inverse orthogonaltransform unit 24 for inverse orthogonal transform to generate adifference picture. The signals of the difference picture produced bythe motion compensation unit 27 are summed together by an adder 25 toproduce picture signals which are stored in a frame memory 28 whilebeing sent to the multiplexer 29.

In the moving picture expansion device of the present first embodimentof the present invention, the multiplexer 29 multiplexes the motionvector information outputted by the motion vector separator 22 in theblanking portion of a picture outputted by the adder 25. The signalshaving the motion vector information multiplexed in a blanking period ofthe picture by the multiplexer 29 are outputted from the picture outputterminal 26.

An illustrative method for multiplexing the motion vector information inthe blanking portion of the picture is now explained.

Since the blanking portion of the picture signals corresponds to theblanking period, it is a picture portion not displayed as a picture. Theblanking is classified into horizontal blanking corresponding to thehorizontal blanking period and vertical blanking corresponding to thevertical blanking period. In the NTSC television broadcasting systememployed in Japan and United States of America, 35 lines per framerepresent vertical blanking, as shown in FIG. 6.

If the picture of the NTSC television broadcasting system is handledwith the MPEG2 standard, the encoded pixels are usually 720 pixels by480 lines, with the motion compensation unit block being 16 pixels by 16lines, termed a macro-block. The number of macro-blocks per frame is(720/16) (480/16)=1350 pixels. The maximum number of the motion vectorper macro-block is four. For representing a motion vector, 16 bits infixed-length representation suffice even if the maximum of ±96 pixelsare taken vertically and horizontally. Therefore, 1350 4 16=86400 bitsare sufficient as a required number of bits for representing the motionvector in one frame.

Also, if 720 pixels in terms of 8 bits are used per line of the verticalblanking of a picture,

8 720=5760 bits/line can be used.

It is seen from above that, if 86400/5760=15 lines of vertical blankingare used per frame, the motion vector can be multiplexed to picturesignals in fixed length representation. Since there are 35 lines ofvertical blanking per frame, this multiplexing is feasible.

Referring to FIG. 7, a moving picture compression device according tothe first embodiment of the present invention is explained.

In the moving picture compressing device of the present invention,picture signals entering a picture input terminal 1 are compressed, andthe compressed picture signals are outputted at a bitstream outputterminal 9.

Referring to FIG. 7, picture signals obtained on multiplexing the motionvector information in the blanking portion by the picture expansiondevice of FIG. 5 are supplied to the picture input terminal 1. Thepicture signals, comprised of the motion vector information multiplexedin the blanking portion, entering the picture input terminal 1, are sentto a motion vector separator 13, which then separates, from the picturesignals supplied from the input terminal 1, the motion vectormultiplexed in the blanking portion, and sends the motion vectorinformation to a motion compensation unit 10 and to a multiplexer 8,while sending the picture signals freed of the motion vector to adifference calculating unit 2.

The motion compensation unit 10, supplied with the motion vectorinformation from the motion vector separator 13, motion compensates thepicture stored in the frame memory 11 based on the motion vector forformulating a prediction picture.

The difference calculating unit 2, fed with the picture signals from themotion vector separator 13, calculates the difference between thepicture signals and the prediction picture formulated by the motioncompensation unit 10. The difference signal as found by the differencecalculating unit 2 is sent to an orthogonal transform unit 3 fororthogonal transform processing. The signal orthogonal transformed bythe orthogonal transform unit 3 is sent to a quantizer 4 forquantization for compression. The quantized data is sent to themultiplexer 8 for multiplexing with the motion vector informationsupplied from the motion vector separator 13. The resulting multiplexedsignal is outputted at a bitstream output terminal 9. The multiplexingoccurs in accordance with for example the MPEG format.

The quantized data from the quantizer 4 is also sent to a dequantizer 5for dequantization and thence supplied to an inverse orthogonaltransform unit 6 for inverse orthogonal transform. This produces adifference picture which is the same as that restored from the outputbitstream. The signal of the difference picture and the signal of theprediction picture formulated by the motion compensation unit 10 aresummed together by the adder 7 to produce picture signals which are thenstored in the frame memory 11.

In the moving picture compression device of the above-described firstembodiment of the present invention, the picture signals with the motionvector multiplexed thereon are entered to the picture input terminal 1,and the motion vector and the picture signals are separated from thepicture signals multiplexed with the motion vector in the motion vectorseparator 13, with the motion vector being sent to the motioncompensation unit 10 and to the multiplexer 8.

With the above-described first embodiment of the moving picturecompression device and moving picture expansion device, since the motionvector multiplexed in the blanking can be used at the time of repeatedcompression and expansion as shown for example in FIG. 4, impropermotion vector can hardly be produced in distinction from theconventional practice in which the motion vector is found in a picturealready compressed and expanded and hence deteriorated in picturequality. The result is the reduced residuals on motion compensation thusassuring efficient prediction. Moreover, the adequate motion vector asin the present embodiment has high correlation and can be representedwith a smaller number of bits thus improving the picture quality evenwith the same bit rate as the conventional bit rate.

Also, with the first embodiment of the present invention, in which themotion vector information is written in the blanking portion f thepicture signals not used for picture display, there is no necessity ofrecording the motion vector in a separate recording medium as isrequired in the conventional practice.

The second embodiment of the present invention is explained. In themoving picture compression device of the present second embodiment,parts or components similar in structure to the first embodiment aredepicted by the same reference numerals. The moving picture expansiondevice as a counterpart device of the moving picture compression deviceof the second embodiment is the same as that of the first embodiment andhence the corresponding description is omitted for simplicity.

In the second embodiment of the present invention, the moving picturecompression device retrieves a more appropriate motion vector forovercoming the drawback that the motion vector laid in store by beingmultiplexed in the blanking portion of the picture signals as describedabove is not necessarily an optimum motion vector. Specifically, withthe present second embodiment of the present invention, the movingpicture compression device includes a motion vector detector 12, asshown in FIG. 8. This motion vector detector 12 retrieves again a moreappropriate motion vector from the input picture based on the motionvector separated from the motion vector separator 13.

In the moving picture compression device of the second embodiment of thepresent invention, shown in FIG. 8, picture signals having the motionvector information multiplexed in the blanking portion thereof by themoving picture expansion device of FIG. 1 are sent to the picture inputterminal 1. The input signal at the picture input terminal 1 is sent tothe motion vector separator 13 where the motion vector is separated. Theresulting motion vector information is supplied to the motion vectordetector 12 while the picture signals freed of the motion vector aresent to the motion vector detector 12 and to the difference calculatingunit 2.

The motion vector detector 12 retrieves again the neighborhood of themotion vector separated by the motion vector separator 13 on the inputpicture and outputs the new motion vector as obtained as the result ofsecond retrieval to the motion compensation unit 10 and to themultiplexer 8. The range of the second retrieval need not be set aslarge as the entire range of the values assumed by the motion vector,that is the entire range of the input picture, but only may be theneighborhood of the motion vector separated by the motion vectorseparator 13. In this manner, there is no risk of increasing the motionvector exhibiting lesser correlation at a position far from a positionindicated by the motion vector separated by the motion vector separator13 thus enabling the motion vector with lesser residuals to be produced.

The motion compensation unit 10 motion compensates the picture stored inthe frame memory 11 based on the motion vector supplied thereto toproduce a prediction picture.

The difference calculating unit 2 calculates the difference between thepicture signals supplied thereto and the prediction picture produced bythe motion compensation unit 10 to transmit the resulting differencesignal to the orthogonal transform unit 3. The signal orthogonaltransformed by the orthogonal transform unit 3 is sent to the quantizer4 for quantization for signal compression.

The quantized data from the quantizer 4 is dequantized by thedequantizer 5 and inverse orthogonal transformed by the inverseorthogonal transform unit 6 for restoring the difference picture signalwhich is then summed by the adder 7 to the signal of the predictionpicture formulated by the motion compensation unit 10. The resultingpicture signals are stored in the frame memory 11 for theabove-mentioned motion compensation.

The multiplexer 8 multiplexes the motion vector information suppliedfrom the motion vector detector 12 to the quantized data from thequantizer 4. The resulting bitstream is outputted at the bitstreamoutput terminal 9 of the moving picture compression device.

The third embodiment of the present invention is explained. In thepresent third embodiment, the information volume of the motion vectorlaid in store in the blanking period can be reduced.

FIG. 9 shows a moving picture expansion device of the present thirdembodiment. In FIG. 9, parts or components which are the same as thoseof FIG. 5 are denoted by the same reference numerals.

In FIG. 9, the bitstream entering the bitstream input terminal 1contains the motion vector detected at the time of encoding the movingpicture as in FIG. 5.

The motion vector separator 22 separates the motion vector informationfrom the bitstream and sends the separated motion vector information toa motion compensation unit 27 and to a motion vector quantizer 30 whilesending the remaining quantized data to a dequantizer 23.

The motion vector quantizer 30 quantizesi the motion vector informationsupplied from the motion vector separator 22 for compression. The motionvector information quantized by the motion vector quantizer 30 is sentto a multiplexer 29.

The motion compensation unit 27 motion compensates the picture in aframe memory 28 based on the motion vector from the motion vectorseparator 22 for constructing a prediction picture.

The dequantizer 23 dequantizes the quantized data. An output of thedequantizer 23 is inverse orthogonal transformed by an inverseorthogonal transform unit 24 to produce a signal of the differencepicture which is summed by an adder 25 to the signal of the predictionpicture produced by the motion compensation unit 27. The picture signalsobtained by the adder 25 are stored in the frame memory 28 while beingsent to the multiplexer 29.

The multiplexer 29 multiplexes the motion vector information quantizedby the motion vector quantizer 30 in the blanking portion of the picturesignals supplied from the adder 25. An output picture signal of themultiplexer 29 is issued at the picture output terminal 26 of thepicture expansion device.

Referring to FIG. 10, a moving picture compression device according to athird embodiment of the present invention, associated with the movingpicture expansion device of FIG. 9, is explained. In FIG. 10, parts orcomponents similar in structure to those of the moving picturecompression device shown in FIG. 8 are depicted by the same referencenumerals.

In FIG. 10, the picture signal obtained on multiplexing the quantizedmotion vector information by the moving picture expansion device of FIG.9 in its blanking portion is entered to the picture input terminal 1.The signal entering the picture input terminal 1 is sent to the motionvector separator 13 where the quantized motion vector is separated. Thequantized motion vector information is sent to the motion vectordequantizer 14, while the picture signals, freed of the quantized motionvector, are sent to the motion vector detector 12 and to the differencecalculation unit 2.

The motion vector dequantizer 14 dequantizes the quantized motion vectorinformation to regenerate the motion vector prior to quantization by themotion vector quantizer 30 of FIG. 9. The motion vector information,obtained by the motion vector quantizer 14, is sent to the motion vectordetector 12.

On reception of the motion vector as found by the motion vectordequantizer 14, the motion vector detector 12 retrieves the neighborhoodof the motion vector on the input picture, as in the moving picturecompression device of the second embodiment, and outputs a new motionvector obtained by the second retrieval to the motion compensation unit10 and to the multiplexer 8.

The motion compensation unit 10 motion compensates the picture stored inthe frame memory 11, based on the motion vector supplied thereto, inorder to formulate a prediction picture.

The difference calculation unit 2 calculates the difference between thesupplied picture signals and the prediction picture formulated by themotion compensation unit 10, and routes the difference signal to theorthogonal transform unit 3. The orthogonal transformed signal from theorthogonal transform unit 3 is sent to the quantizer 4 where it isquantized for signal compression.

The quantized data from the quantizer 4 is dequantized by thedequantizer 5 and inverse orthogonal transformed by the inverseorthogonal transform unit 6 to restore the difference picture signalwhich is summed by the adder 7 to the signal of the prediction pictureproduced by the motion compensation unit 10. The picture signalsobtained by the adder 7 are stored in the frame memory 11 for theabove-mentioned motion compensation.

The multiplexer 8 multiplexes the motion vector information suppliedfrom the motion vector detector 12 to the quantized data from thequantizer 4. The bitstream, thus produced, is outputted at the bitstreamoutput terminal 9 of the moving picture compression device.

In the present third embodiment, the motion vector information obtainedby the motion vector dequantizer 14 may be directly sent to the motioncompensation unit 10 and to the multiplexer 8 without providing themotion vector detector 12.

However, if the motion vector is retrieved again as described above, itbecomes possible to obtain the motion vector with smaller residuals, asdiscussed in connection with the second embodiment, such that thereresults no inconvenience if the motion vector precision is lowered byquantizing the motion vector by the moving picture compression device,but the merit of the present embodiment in reducing the code volume formotion vector can be manifested more effectively. In this manner, themajor portion of the banking portion of the picture signals can be usedfor objects other than laying the motion vector in store, thus enablingcompression and expansion with higher picture quality.

In the above-described second and third embodiments, the motion vectoror the quantized motion vector may be laid in store not only in theblanking portion of the picture signals, as in the first embodiment, butmay be recorded on various recording mediums, such as tape-shaped ordisc-shaped recording medium or on a memory. If, for example, a digitalvideo cassette (DVD) is used, the motion vector or the quantized motionvector may be laid in store in a memory enclosed in the cassette,whereas, if a non-linear editing unit is used, the information may belaid in store in a hard disc. In this case, since the recording mediumsas described above are required for laying the motion vector or thequantized motion vector in store, it is desirable to lay the informationin store in the blanking in the second and third embodiments as in thefirst embodiment as described above.

In the description of the previous embodiments, the motion vector isdirectly encoded with a fixed length. However, variable length codingmay also be used for further decreasing the data volume multiplexed inthe blanking portion.

Moreover, in the above-described embodiments, the motion vector ismultiplexed in the blanking of the picture signals. It is howeverpossible to multiplex not only the motion vector but also the picturecoding type information in the MPEG standard, the information on thefield/frame construction types, information on the demarcation of thegroup-of-pictures (GOPs) or the scene-change information. If the aboveinformation is multiplexed, it becomes possible to produce a picture ofhigher sound quality at the time of repeated compression/expansion.

In the above-described embodiments of the present invention, the motionvector used in the picture expansion device is multiplexed in theblanking portion of picture signals, while the moving picturecompression device effects picture compression using the motion vectormultiplexed in the blanking portion, so that there is no risk of usingan inappropriate motion vector even on the occasion of repeatedcompression/expansion, thus realizing efficient encoding with littleresiduals on motion compensation. The adequate motion vector has highcorrelation so that the code volume for representation of the motionvector can be diminished thus improving the picture quality for the samebit rate. Moreover, in the second embodiment, it becomes possible toretrieve magneto-resistance effect appropriate motion vector and to usethe resulting appropriate motion vector. In the third embodiment, theinformation volume for the motion vector can be quantized for reducingits volume. These merits can be realized without using separate datastorage means.

What is claimed is:
 1. A moving picture compression device comprising:motion vector separating means for receiving an expanded motion picturesignal that had been produced by multiplexing an expanded moving picturesignal with a motion vector that was used for the expansion of saidmoving picture signal, and for separating a received motion vector fromthe received expanded motion picture signal; and compression means forcompressing the received expanded motion picture signal using theseparated motion vector.
 2. A moving picture compression devicecomprising: motion vector separating means for receiving an expandedmotion picture signal that had been produced by multiplexing an expandedmoving picture signal with a motion vector that was used for theexpansion of said moving picture signal, and for separating a receivedmotion vector from the received expanded motion picture signal; motionvector detection means responsive to the separated motion vector fordetecting, from the received expanded motion picture signal freed of themultiplexed motion vector, a new motion vector in the neighborhood ofthe separated motion vector; and compression means for compressing thereceived expanded motion picture signal using the new motion vector. 3.A moving picture compression device comprising: motion vector separatingmeans for separating from a received moving picture signal a motionvector multiplexed in a blanking portion in the received moving picturesignal; wherein said motion vector is separated from said blankingportion before compression and expansion, and is used for compressionand expansion when repeated compression and expansion of said receivedmoving picture signal is to occur; motion vector detection meansresponsive to the separated motion vector for detecting, from thereceived moving picture signal freed of the multiplexed motion vector, anew motion vector in the neighborhood of the separated motion vector;and compression means for compressing the received moving picture signalusing the new motion vector.
 4. A moving picture expansion device forexpanding a compressed motion picture signal comprising: motion vectorseparating means for separating from the compressed motion picturesignal a motion vector appended thereto; expansion means for expandingthe compressed motion picture signal using the separated motion vector;and multiplexing means for multiplexing the separated motion vector in ablanking portion in a received moving picture signal with the expandedmotion picture signal; wherein said motion vector is separated from saidblanking portion before compression and expansion, and is used forcompression and expansion when repeated compression and expansion ofsaid received moving picture signal is to occur.